This invention relates to a nozzle device including a housing having an inlet intended for a fluid and an orifice for spraying a firm jet of fluid, which orifice is delimited by two or more members, at least one of which is movable relative to the other one between a first position in which the orifice has a minimal cross-section area in order to spray out the fluid in a firm jet in a direction forwards from the house, and a second position in which the orifice nozzle is widened in order to be flushed clean by means of a coarse stream of fluid.
A nozzle device of the art stated above is previously known by SE 9302283-8 (publ. no. 502 051). This nozzle device is particularly advantageous in comparison with conventional nozzles having an invariable diameter in so far as the nozzle device may be flushed clean during operation by the simple measure of widening the hole for a limited time, e.g., some seconds. In practice, such nozzle devices are chiefly used for spraying liquid, such as water. Although the nozzle devices may be utilized in miscellaneous sprinkling systems, the same are particularly suitable for such sprinkling systems which occur in the paper and pulp industry, and have the purpose of keeping filters and strainers clean. In such applications, the nozzle devices are usually furnished with a spoon-like member in front of the orifice, towards which member the firm jet of water is directed and reshaped to a flat and sector-shaped stream or curtain.
During practical operation it has turned out that the indeed short, but extraordinary forceful flow of water which arises when the orifice is widened in order to be cleaned, may damage the objects being sprayed. In case the ordinary firm and thin jet of water has the purpose of keeping clean, for instance, a weak filter, this filter may partially disintegrate when the nozzle device is reset and the coarse stream of flushing water hits the same with a high impact.
The present invention aims at rectifying the above-mentioned drawback of the nozzle device known by SE 9302283-8 and at providing an improved nozzle device. Therefore, a primary object of the invention is to create a nozzle device which, on one hand, allows unrestricted spraying of a firm or thin jet of fluid, but which prevents that a forceful stream of flushing fluid is directed towards the object being sprayed in connection with resetting of the device for flushing clean the orifice. An additional object is to provide a nozzle device in which the short, periodical flows of flushing fluid may be utilized for flushing clean the spraying system in which the nozzle device is included, in particular the piping in which the fluid is fed to the nozzle device.